Number of collisions per collision pair

Now the number of collisions is calculated per species pair. This allows
that the randomly particles selected for collisions do not have
collisions assigned.

src/modules/mesh/1DCart/moduleMesh1DCart.f90

@@ -220,6 +220,9 @@ MODULE moduleMesh1DCart
 
       CALL OMP_INIT_LOCK(self%lock)
 
+      ALLOCATE(self%listPart_in(1:nSpecies))
+      ALLOCATE(self%totalWeight(1:nSpecies))
+
     END SUBROUTINE initVol1DCartSegm
 
     !Calculates a random position in 1D volume